This invention relates to an improvement in tightly sealed paperboard cartons and, more particularly, to a tubular carton having tightly sealed ends.
Paperboard cartons are an inexpensive and convenient method for storage, shipment and display of almost any type of product. However, where the carton contents include or comprise finely divided material, such as powders or granulated material, it is necessary that the end closures of the carton be tightly sealable. Such seal is necessary both to keep the contents from sifting out through the seams and, in the case of food products, to prevent insects from gaining entry into the carton.
Commonly, this problem is overcome by providing the carton with an internal bag closure, or by overwrapping the carton with a paper wrapper or a cellophane film. Such methods, however, add to the complexity of filling and sealing the cartons, to the cost of the packaging and to the shipping weight of the filled package.
Embossing of end flaps so that they lie in closer relationship is also common, as described in U.S. Pat. Nos. 3,003,677 and 3,934,791. This solution, however, requires a substantial overlapping of the carton end flaps and, therefore, the use of an excessive amount of paperboard material.
It is, therefore, a primary object of the present invention to provide a tubular carton having ends more effectively sealed than those of conventional cartons. This is accomplished, in general, by a carton having two end flaps with debossed portions, a third end flap with an embossed portion, and a fourth planar, end flap captured between the debossed and embossed flaps. More specifically, the debossed end flaps comprise an opposed pair connected to the narrower side panels of the carton, while the embossed and planar end flaps are connected to the relatively wider front and back panels respectively.
It is another object of the invention to provide a carton as above-described, which requires a minimum amount of paperboard. This is accomplished by reducing the length of three of the end flaps, as compared to those of a conventional carton of the same overall size. Such reduction is possible because the superior end closure of the present invention, wherein one end flap is captured between the others, eliminates the need for the substantial flap overlap heretofor required for effective sealing.
Sealing of the present end closure is effected by first folding the debossed end flaps to a position perpendicular to the carton side panels. The planar end flap is then folded so as to rest on the debossed end flap portions. Finally, the embossed flap is brought into juxtaposition with the other three flaps, whereupon the embossed portion thereof overlies the planar flap.